<!DOCTYPE html>
<html>
    <head>
        <style>
            * {
                margin: 0;
                padding: 0;
            }
            body {
                background-color: black;
            }
            div.wrapper {
                position: relative;
                height: 5000px;
            }
            div.d {
                width: 50px;
                height: 50px;
                position: absolute;
            }
            .left {
                left: 0;
            }
            .right {
                right: 0;
            }
            .top {
                top: 0;
            }
            .bottom {
                bottom: 0;
            }
            .red {
                background-color: rgb(255, 0, 0);
            }
            .green {
                background-color: rgb(0, 255, 0);
            }
        </style>
    </head>
    <body>
        <div class="wrapper">
            <div class="d left top red"></div>
            <div class="d right top green"></div>
            <div class="d left bottom green"></div>
            <div class="d right bottom red"></div>
        </div>
    </body>
</html>
